Thioredoxin-Linked Changes in Enzymes and Storage Proteins

点击翻译按钮获取中文摘要

Buchanan 9316496 This proposal is based on recent evidence that the NADP/thioredoxin system (consisting of thioredoxin h, NADP-thioredoxin reductase and NADPH) functions in seed germination. Thioredoxin specifically reduces major storage proteins of cereals (gliadins and glutenins in wheat), thereby enhancing their solubility and susceptibility to proteinases, and reductively inactivates a disulfide protein that inhibits alpha-amylase, an enzyme of starch degradation (barley alpha-amylase/subtilisin inhibitor). An extension of this research has shown that the thioredoxin system strengthens the gluten protein network, thereby enhancing bread quality, and inactivates trypsin inhibitor proteins, thereby potentially improving the nutritional quality of soybean. A patent application covering these findings has been filed, and precommercial development of thioredoxin technology has commenced. The proposed research addresses fundamental new questions: (1) Does thioredoxin have additional regulatory functions in the germination of cereals such as wheat? (2) What changes in redox state and abundance does thioredoxin undergo during germination? (3) Does the activity of enzymes necessary for the reduction of thioredoxin change during germination? (4) Does thioredoxin function in the germination of other types of seeds such as soybean?. The research will add to our understanding of thioredoxin function, enzyme regulation and seed germination. %%% This proposal stems from research in which we have presented evidence for an enzyme system (the "thioredoxin system") that functions as the earliest known signal triggering the germination of cereals such as wheat. The thioredoxin system functions by (1) activating storage proteins of the grain, thereby enabling their use as a source of nitrogen and energy by the seedling, and (2) activating enzymes required for the degradation of starch, thereby enhancing energy production in the early phase of germination. An extension of this research indicates that the thioredoxin system is of technological value. Application of the system to flour strengthens gluten and enhances bread quality. The thioredoxin system also neutralizes plant protein inhibitors of animal digestive enzymes. Application of the thioredoxin system to foods like soybean may enhance their nutritional quality. A patent application covering these uses has been filed, and precommercial development of thioredoxin technology has commenced. The current project represents an extension of the fundamental aspects of this research. The experiments planned will show whether the thioredoxin system has additional functions in wheat and whether the system is important in the germination of other seed types. ***